Set piece ... The Truman Show, the Hollywood movie which was filmed in Seaside, a Florida community designed by Duany. Photograph: Melinda Sue Gordon/Paramount

One of Prince Charles's allies in his battle against modern architecture has attacked the "disappointing to dismal" design of British postwar towns.

Sparking anger among architects, Andres Duany flew in from America and yesterday unveiled a 64-point litany of mistakes made by British architects and planners over the last 50 years.

He accused architects of being "infantile" in pursuing ego-driven visions and said they were "heedless of technical and social dysfunction and widespread lack of popularity" caused by their designs.

Duany is one of the original designers of Poundbury, the prince's new town in Dorset, and said the leading lights of modernist architecture including Richard Rogers, Frank Gehry, Zaha Hadid and Peter Eisenman were "increasingly irrelevant".

He called on architects and planners to step aside and allow a new generation of amateurs to lead development in the 21st century.

The broadside was met by a vociferous response from leading modern architects who have become used to regular disputes with the prince and his allies. Sunand Prasad, president of the Royal Institute of British Architects, said Duany was "living in another world".

He conceded that architects' craft skills and traditional knowledge had been swept aside too easily between the 1950s and 1970s, but said architects were now building the "highest performance" buildings ever.

Duany's outburst, will reignite a battle between architects who believe in modernism and his own "church" of new urbanism, which argues that towns should be built to strict codes, often based on traditional design.

Duany used new urbanism to design Seaside, the Florida community which provided the backdrop to the film The Truman Show, and Charles has embraced the principles of new urbanism on projects to design new settlements from Newquay, Cornwall to Llandarcy, near Neath.

His intervention was timed to coincide with the unveiling of a masterplan for Hertfordshire, his most ambitious UK scheme yet. In it he advocates a new town and a series of garden villages built on open land in which residents would be obliged to grow fruit and vegetables for market.

"It is inexplicable why architects and planners continue to pursue radical innovation as if it were 1945 every morning," he said.

"Only architecture, confusing itself with fashion as a platform for cultural expression, continues to be avant garde, heedless of its cost overruns, social and technical dysfunction and widespread lack of popularity."

He cited "gratuitous shapes" in buildings such as winged roofs which quickly go out of fashion, "amazingly rude" colours on shop signs which "are just a vulgar way to attract attention" and civic buildings that "look common" when they should be grand.

Out-of-town retail parks, excessive road signage and "placeless architecture that could be anywhere in the world" were also criticised. Duany advocates a return to "matter of fact architecture" as exemplified by the traditional English village.

Prasad said it was "obviously untrue" that the majority of architects want to express themselves regardless of context. "It is not so much the innovation and the ego that is causing the problem," he said.

"It is the commercial pressure to build large on sites which can't take it; it is the haphazard development of towns and the widespread confusion over our democratic planning process."

Prasad said many of Duany's complaints seemed to stem from the decision to build a car-based society, and the way highways engineers took control of urban design.

"It was wrong to aim for a society dominated by cars," he said.

"But most architects and planners have moved on, so he is really railing against a problem that doesn't exist anymore."

What not to do

• Avoid fashionable architecture - buildings that are obsessively of our time will be out of date too soon

• Civic buildings should be grand and private buildings should recede into the background